The fact is that the ADA will ONLY allow the test taker to take one or two parts over. Only if he or she has received an over all passing score of 75. I have never personally heard of passing and having to take two parts over the majority of test takers pass and take one part over. This is however, the law/rule that governs the test. There are no exceptions. However, if you did pass and are not happy with your results then you are only eligible to take the whole exam over and not just the areas that you feel you did not do well in.
Remember, we all need the magical 90 or better, but if you get less then that your options are as follows:
1) Take the exam over, this is the norm and recommended.
2) If you receive a total passing grade of 84-89; apply first to all your programs that you want to and while preparing to retake the whole exam over, pray that you do well enough in the interview and have at least a GPA of 3.0 or better then wait for the acceptance. If you don't get in any where, then take part 1 over with having not wasted any time.
3) If you get an 80-84 try applying to all the Universities that have P. G or Ms. programs and that only want part 1 then apply. Also, study and take part two this will better your chances of getting into said programs.
These are my opinions and are subject to scrutiny and non support. What I have stated to you are the facts as I know them to be . - Bill